Variable impedance coaxial line



July 4, 1961 L. YOUNG ETAL 2,991,435

VARIABLE IMPEDANCE COAXIAL LINE Filed Feb. 19, 1960 2 h ets-Sheet 1 IN V EN TORS 0 Fad/V6 Ali/7P4 in TA 775? By g? M! July 4, 1961 L. YOUNG ETAL VARIABLE IMPEDANCE COAXIAL LINE 2 Sheets-Sheet 2 Filed Feb. 19, 1960 INVENTORS .450 yaw/r6 A:

. istic impedance.

United States Patent VARIABLE IMPEDANCE COAXIAL LINE Leo Young and Francis J. Rutter, Baltimore, Md., as-

signors, by mesne assignments, to the United States of merica as represented by the Secretary of the Air orce Filed Feb. 19, 1960, Ser. No. 10,004 Claims. (Cl. 333-97) I The present invention relates to coaxial transmission lines and more particularly to a coaxial line having variable characteristic impedance.

It is. frequently desired to have an impedance matching section in a coaxial transmission line. In the simplest form, this may be realized by the insertion of an adjustable element in the transmission line in such a manner as to be parallel to the electric field. A more common device, in the prior art, is a stub with a sliding plunger. This is more effective but becomes bulky for large coaxial transmission lines, such as are necessary at very high powers.

The present invention is of general application but is particularly useful where space is limited, and where very high power must be transmitted. In the embodiment of the invention as herein illustrated, a section of coaxial transmission line having concentric inner and outer conductors is caused to have susceptibility of regulation of the diameter of the inner conductor while .retaining the concentric relationship. There is also included the capability of varying the diameter of the'outer conductor while retaining the concentric relationship with the outer conductor. An additionalimportant feature of thepresent invention resides in the concept of simultaneous variation of the diameters of both the inner and outer conductors, while retaining their concentric relationship. The variations in the eifective diameters of'the aforesaid inner and outer conductors in turn varies the'characteristic impedance of the coaxial transmission line.

The various features of novelty which characterize this invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages and specific objects obtained with its use, reference should be had to the accompanying drawings and descriptive matter in which is illustrated and described the present invention.

Of the drawings: 9

FIGURE 1 illustrates a cross-sectional view of a coaxial transmission line having variable characteristic impedance;

FIGURE 2 is an elevation view partially in section showing the control mechanism for aforesaid variations; and

FIGURE 3 is an axially displaced end view partially cut away of control elements as shown in FIGURE 2.

Referring now to FIGURE 1, there is shown a crosssectional view of a coaxial transmission line which serves as a quarter wave transformer of a variable character- There is provided an inner and outer conductor assembly. The inner conductor assembly is comprised of inner metal supporting cylinder and a series of fingers integrated therewith and hereinafter described and referred to as Phosphor bronzestrips 12-17. The outer conductor assembly is comprised of outer metal supporting cylinder 11 and a series of fingers integrated therewith and hereinafter described and referred to ,as Phosphor bronze strips 66-71. For the purposes of this exposition, the diameter of the inner metal cylinder 10 'may be assumed to be about five inches and the outer a pipe of about three inches in diameter.

2,991,435. Patented July 4., 1961 2 ing cylinder 10 is concentric to outer supporting cylinder 11. Six strips of Phosphor bronze 12-17 are utilized, each of which is four inches wide and of the required length. Each of the strips was preformed to fit around Strips 12-17 were then laid around inner cylinder 10. Each of one of the outer extremities of strips 12-17 is anchored at each of points 18-23, respectively. The anchoring may be accomplished by welding or any other suitable conventional means. Each of the outer extremities of each of strips 12-17 is formed into contact spring fingers 24- 29, respectively, which ride piggyback style on the next succeeding strip as shown in FIGURE 1. 'In effect each strip is anchored at one end with the opposite end arranged slidably to contact an adjacent strip.

Each of screws 30-35 is inserted through each of holes 36-41, respectively, of cylinder 10. One end of each of screws 30-35 is soldered to each of strips 12-17 at each of the points 42-47, respectively. The other end of each of screws 30-35 is connected to each of adjusting wires 48-53, respectively. Each of self-locking nuts 54-59 is fixed on each of screws 30-35, respectively, and is utilized to control the distance each of the strips can project between inner and outer cylinders 10 and 11.

A similar system for varying the outer diameter is utilized and is shown in detail by reference to outer cylinder 11 and associated elements. Six strips of Phosphor bronze 66-71 are utilized. Each of the strips is four inches wide and of the required length. Each of one of the outer extremities '72-77 is anchored at each of the points 81-86, respectively. The anchoring may be accomplished by .welding or any other suitable conventional means. Each of the other outer extremities 87- 92 of each of strips 66-71, respectively, is formed into a contact spring finger which rides piggyback style on the next succeeding strip. Thus each strip is anchored at one end with the-opposite end arranged slidably to contact an adjacent strip.- J

Each of screws 93-98 is inserted through each of holes 99-104, respectively, of outer cylinder 11. One'end of each of screws 93-98 is soldered to each of strips 66-71 at points -110, respectively. The other end of each of screws 93-98 is connected to each of adjusting wires 111-116, respectively. Each of self-locking nuts 117- 122 is fixed on screws 93-98, respectively, and is utilized to control the distance that strips 66-71 may extend-between inner and outer cylinders 10 and 11.

There is presently provided adjusting wires 48-53 for Phosphor bronze strips 12-17, respectively. When the aforesaid adjusting wires are pulled simultaneously, their associated strips would move inwardly and thus change the diameter of the inner conductor which is comprised of the aforesaid strips. When the adjusting wires are released, the Phosphor bronze springs 12-17 would return to their original position because they are eifectively spring-like in their action. In a similar fashion, when adjusting wires 111-11'6 are pulled simultaneously, their associated Phosphorbronze strips 66-71, respectively, are moved. Thus the outer conductor which is comprised of strips 66-71 changes diameter. Upon releasing adjusting wires 111-116, strips 66-71, respectively, would return to their original position because of their spring-like action. It is to be noted that the diameter of both inner and outer conductors could also be varied simultaneously by controlling the aforesaid adjusting Wires. There is thus provided means for varying the diameters of the inner and outer conductors of a coaxial transmission line while retaining at all times a concentric relationship therebetween. I

Referring now to FIGURE 2 in detail, there is shown control means for controlling the adjusting wires hereinbefore described. There is also shown in conjunction metal disc 21.

is described in detail hereafter.

means to control the aforesaid adjusting wires may be utilized and is of secondary importance. the ad usting wires may be tied to the rim of a disc,

For example.

which can be turned about the axis of the coaxial line.

Outer metal cylinder 11 is concentric to inner metal cylinder 10 and the concentric cylinders are closed at one end by insulating disc 120 and at the other end by Phosphor bronze strips 66 and 69 are only shown but what is said as to them applies equally to the control strips 66-71. Adjusting wires 111 and 114 are utilized to pull bronze strips 66 and 69, respectively, toward outer cylinder 11. Self-locking nuts 117 and 120 control the maximum distance that spring-like bronze strips 66 and 69, respectively, can extend towards inner cylinder 10. The adjusting wire 111 leads through pulleys 122, 123 and 133 and is held by clamp adapter 126 to slidable post 127 by means of screw 128 or other similar means. Adjusting wire 14 leads through pulleys 123, 125 and 133 and is held also by clamp adapter 126 to post 127 by means of screw 128. In the same fashion,

pull wires 42-47 and 111-116 and thus in turn vary the position of bronze strips 12-17 and 66-71, respectively, Annular locating'ring 137 is affixed to the quarter wave transformer by screws. Annular mounting plate 138 is integrated with annular locating ring 137. Bearing 139 guides post 127 and bearing 140 guides post '135. Bearing 141 houses rtatable hand control worm shaft 142 which has hand wheel 143 aflixed thereto by means of washer 144 and nut 145. Wheel 143 is turned by handle 146. Worm shaft 142 is held in bearing 141 by pin 147 which allows shaft 142 to turn as pin 147 engages groove 148 of shaft 142. Bearings 139, 140 and 141 are afiixed to mounting plate 137 by conventional means such as socket-head cap screw 151.

The longitudinal movement to pull or release aforesaid adjusting wires attached to post 127 is accomplished by engaging segmental internal threaded rider gear 149 by means of handle 152 and by locking headless set screw 153 rigidly to post 127 thereby relaying the movement of rider 149 to post 127 and thereby to the adjusting wires attached thereto. This movement is accomplished by turning wheel 143.

A similar control of adjusting wires 111-116 is achieved by transferring longitudinal motion obtained from engaging segmental worm gear of rider 150 to worm shaft 142 by locking rider 150 to post 135 by set screw 155 and then turning wheel 143.

When both riders 149 and 150 are engaged and wheel 143 is rotated, then adjusting wires 111-116 and 42-47 are pulled simultaneously. If rider 150 is disengaged and wheel 143 is rotated then adjusting wires 111-116 will only be pulled whereas if rider 149 is disengaged and wheel 143 is rotated then adjusting wires 42-47 will be pulled. When both riders 149 and 150 are disengaged the pull on adjusting wires 42-47 and 111-116 is released and thereby, because of spring-like action of strips 12- 17 and 66-71, respectively, the aforesaid strips return to their original positions as determined by their associated self-locking nuts 54-59, and 117-122, respectively.

It is thus seenthat the inner conductor of the quarter wave coaxial transformer is comprised of bronze strips 12-17 and the outer conductor of bronze strips 66-71. The positions of strips 12-17 and 66-71 are controlled by adjusting wires 42-47 and 111-116 as they are affixed thereto by means of screws 30-35 and 93-99, respectively. Adjusting wires 42-47 are so connected that they arepulled simultaneously and thereby alter the diameter of the inner conductor. Adjusting wires 111- 116 are also connected in a similar fashion so as to be pulled simultaneously and thereby vary the diameter of the outer conductor. Means are also provided whereby adjusting wires 42-47 and 111-116 are pulled at the same instant and thereby alter the diameters of aforesaid inner and outer conductors simultaneously.

FIGURE 3 shows still further the independent selectivity of riders 1'49 and to manipulate the adjusting wires 11'1-116 and 42-47, respectively, as hereinbefore described.

What is claimed is:

l. A variable characteristic impedance coaxial transmission line comprising concentric inner andouter conductors forming a coaxial transmission line, first means to vary the diameter of said inner conductor while retaining said inner conductor concentric to said outer conductor, second means to vary the diameter of said outer conductor while retaining said outer conductor concentric to said inner conductor, and means external to said coaxial transmission line to selectively operate singly and in combination said first and second means, said operating means selectively varying the characteristic impedance of said coaxial transmission line.

2. A variable characteristic impedance coaxial transmission line comprisingan inner conductor assembly concentric to an outer conductor assembly forming a coaxial transmission line, andmeans external to said inner and outer conductor assemblies to selectively vary singly and in combination the diameters of said inner and outer conductor assemblies while retaining said concentric relationship, said selective means Operating to vary the characterstic impedance of said coaxial transmission line.

El. A variable characteristic impedance coaxial transmission line as defined in claim 2 wherein said inner conductor assembly includes adjustable metal fingers integrated therewith.

4. A variabale characteristic impedance coaxial line as defined in claim 2 wherein said outer conductor assembly includes adjustable metal fingers integrated therewith.

5. A variable characteristic impedance coaxial trans mission line comprising a variable inner conductor as sembly concentric to a variable outer conductor assembly forming a coaxial transmission line, said inner and outer conductor assemblies including adjustable metal fingers integrated therewith, and means external to said inner and outer conductor assemblies to selectively vary singly and in combination the diameters of said inner and outer concentric conductor assemblies while retaining said concentric relationship, said external means operating to vary the characteristic impedance of said coaxial transmission line.

References Cited in the file of this patent UNITED STATES PATENTS 2,410,109 Schelling Oct. 29, 1946 2,473,777 Beechlyn June 21, 1949 2,487,619 Usselman Nov. 8, 1949 2,551,672 Harris et a1. May 8, 1951 2,562,323 Martin July 31, 1951 

